Fuel cell system

Abstract

A fuel cell system includes a fuel cell, a fuel gas passage, and an oxidant gas passage. The fuel cell includes a solid polymer membrane, a fuel electrode, and an oxidant electrode. A coolant flows into the fuel cell via a coolant passage to adjust a temperature of the fuel cell. An oxidant gas outlet temperature detector is configured to detect an outlet temperature of an oxidant gas discharged from an outlet of the oxidant gas passage. A coolant temperature detector is configured to detect a temperature of the coolant passing through an inlet or an outlet of the coolant passage. A dry-up controller is configured to decide that the solid polymer membrane is in a dry-up state when a temperature difference between the temperature of the coolant and the outlet temperature of the oxidant gas exceeds a first threshold value.

What is claimed is: 
     
       1. A fuel cell system comprising:
 a fuel cell to generate electric power using a fuel gas and an oxidant gas supplied to the fuel cell, the fuel cell comprising:
 a solid polymer membrane; 
 a fuel electrode; and 
 an oxidant electrode; 
 
 a fuel gas passage through which the fuel gas passes along the fuel electrode in the fuel cell; 
 an oxidant gas passage through which the oxidant gas passes along the oxidant electrode in the fuel cell; 
 a coolant passage via which a coolant flows into the fuel cell to adjust a temperature of the fuel cell; 
 an oxidant gas outlet temperature detector connected to the oxidant gas passage to detect an outlet temperature of the oxidant gas discharged from an outlet of the oxidant gas passage; 
 a coolant temperature detector connected to the coolant passage to detect an outlet temperature of the coolant passing through an outlet of the coolant passage; and 
 an electric control unit programmed to control components of the fuel cell, said electric control unit being programmed to receive the outlet temperature of the oxidant gas detected by the oxidant gas outlet temperature detector and the outlet temperature of the coolant detected by the coolant temperature detector, the electric control unit including a dry-up controller programmed to determine that the solid polymer membrane is in a dry-up state when a temperature difference between the outlet temperature of the coolant and the outlet temperature of the oxidant gas exceeds a stack dry-up decision threshold value that is set to a point in which the outlet temperature of the coolant is slightly higher than the outlet temperature of the oxidant gas. 
 
     
     
       2. The fuel cell system according to  claim 1 ,
 wherein the dry-up controller increases flow rate of the coolant passing in the coolant passage when the dry-up controller decides that the solid polymer membrane is in the dry-up state. 
 
     
     
       3. The fuel cell system according to  claim 1 , further comprising:
 a coolant heat exchanger connected to the coolant passage to adjust the temperature of the coolant passing through the coolant passage; and 
 a fan to deliver air toward the coolant heat exchanger to cool the coolant, 
 wherein the dry-up controller increases a rotational speed of the fan when the dry-up controller decides that the solid polymer membrane is in the dry-up state. 
 
     
     
       4. The fuel cell system according to  claim 2 , further comprising:
 a coolant heat exchanger connected to the coolant passage to adjust the temperature of the coolant passing through the coolant passage; and 
 a fan to deliver air toward the coolant heat exchanger to cool the coolant, 
 wherein the dry-up controller increases a rotational speed of the fan when the dry-up controller decides that the solid polymer membrane is in the dry-up state. 
 
     
     
       5. A fuel cell system comprising:
 a fuel cell to generate electric power using a fuel gas and an oxidant gas supplied to the fuel cell, the fuel cell comprising:
 a solid polymer membrane; 
 a fuel electrode; and 
 an oxidant electrode; 
 
 a fuel gas passage through which the fuel gas passes along the fuel electrode in the fuel cell; 
 an oxidant gas passage through which the oxidant gas passes along the oxidant electrode in the fuel cell; 
 a coolant passage via which a coolant flows into the fuel cell to adjust a temperature of the fuel cell; 
 oxidant gas outlet temperature detecting means for detecting an outlet temperature of the oxidant gas discharged from an outlet of the oxidant gas passage; 
 coolant temperature detecting means for detecting an outlet temperature of the coolant passing through an inlet or an outlet of the coolant passage; and 
 means for deciding that the solid polymer membrane is in a dry-up state when a temperature difference between the outlet temperature of the coolant and the outlet temperature of the oxidant gas exceeds a stack dry-up decision threshold value that is set to a point in which the outlet temperature of the coolant is slightly higher than the outlet temperature of the oxidant gas. 
 
     
     
       6. The fuel cell system according to  claim 1 , wherein the stack dry-up decision threshold value is about 1° C. 
     
     
       7. The fuel cell system according to  claim 5 ,
 wherein the means for determining increases flow rate of the coolant passing in the coolant passage when the means for determining decides that the solid polymer membrane is in the dry-up state. 
 
     
     
       8. The fuel cell system according to  claim 7 , further comprising:
 a coolant heat exchanger connected to the coolant passage to adjust the temperature of the coolant passing through the coolant passage; and 
 a fan to deliver air toward the coolant heat exchanger to cool the coolant, 
 wherein the means for determining increases a rotational speed of the fan when the means for determining decides that the solid polymer membrane is in the dry-up state. 
 
     
     
       9. The fuel cell system according to  claim 5 , further comprising:
 a coolant heat exchanger connected to the coolant passage to adjust the temperature of the coolant passing through the coolant passage; and 
 a fan to deliver air toward the coolant heat exchanger to cool the coolant, 
 wherein the means for determining increases a rotational speed of the fan when the means for determining decides that the solid polymer membrane is in the dry-up state. 
 
     
     
       10. The fuel cell system according to  claim 5 , wherein the stack dry-up decision threshold value is about 1° C. 
     
     
       11. A method of operating a fuel cell system, the fuel cell system including: a fuel cell to generate electric power using a fuel gas and an oxidant gas supplied to the fuel cell, the fuel cell including a solid polymer membrane, a fuel electrode, and an oxidant electrode; a fuel gas passage through which the fuel gas passes along the fuel electrode in the fuel cell; an oxidant gas passage through which the oxidant gas passes along the oxidant electrode in the fuel cell; and a coolant passage via which a coolant flows into the fuel cell to adjust a temperature of the fuel cell, said method comprising
 detecting an outlet temperature of the oxidant gas discharged from an outlet of the oxidant gas passage; 
 detecting an outlet temperature of the coolant passing through an outlet of the coolant passage; and 
 determining that the solid polymer membrane is in a dry-up state when a temperature difference between the outlet temperature of the coolant and the outlet temperature of the oxidant gas exceeds a stack dry-up decision threshold value that is set to a point in which the outlet temperature of the coolant is slightly higher than the outlet temperature of the oxidant gas. 
 
     
     
       12. The method according to  claim 11 , further comprising:
 increasing a flow rate of the coolant passing in the coolant passage when the solid polymer membrane is determined to be in the dry-up state. 
 
     
     
       13. The method according to  claim 12 , further comprising:
 providing a coolant heat exchanger connected to the coolant passage to adjust the temperature of the coolant passing through the coolant passage; 
 providing a fan to deliver air toward the coolant heat exchanger to cool the coolant; and 
 increasing a rotational speed of the fan when the solid polymer membrane is determined to be in the dry-up state. 
 
     
     
       14. The method according to  claim 11 , further comprising:
 providing a coolant heat exchanger connected to the coolant passage to adjust the temperature of the coolant passing through the coolant passage; 
 providing a fan to deliver air toward the coolant heat exchanger to cool the coolant; and 
 increasing a rotational speed of the fan when the solid polymer membrane is determined to be in the dry-up state. 
 
     
     
       15. The method according to  claim 11 , wherein the stack dry-up decision threshold value is about 1° C.